the alkali metals are a group of oxidation metals that decrease in melting point down the group. Halogens are non-metals that get coloured in colour and less reactive down the group. the transition elements in the middle of the periodic table. hey are metals with very high melting points and densities. they form soft compounds in which they have a variety of darker states.

A couple of examples follow:
"Halogens are non-metals that get coloured in colour and less reactive down the group." I would have stated it a little differently, something like this.
"Halogens are non-metals that become coloured and less reactive as one moves down the group." and

the transition elements in the middle of the periodic table. hey are metals with very high melting points and densities. they form soft compounds in which they have a variety of darker states.
the needs to start with a capital letter. You end the sentence with a period at table but that isn't a complete sentence. Then you pick it up with they (mispelled) which makes a sentence that is not good grammar; i.e., "the transition metals in the middle of the table, they are metals...." Then the next sentence starts with a lower case letter (they), etc. I'm not a good grammarian but we need to try to do better.